Cross-cultural adaptation and psychometric testing of the Dutch and German versions of the Evaluation of Daily Activity Questionnaire in people with rheumatoid arthritis

The Evaluation of Daily Activity Questionnaire (EDAQ) is a detailed patient-reported outcome measure of activity ability.The objective of this research was to assess the linguistic and cross-cultural validity and psychometric properties of theEDAQ in rheumatoid arthritis for Dutch and German speakers. The EDAQ was translated into Dutch and German usingstandard methods. A total of 415 participants (Dutch n = 252; German n = 163) completed two questionnaires about fourweeks apart. The first included the EDAQ, Health Assessment Questionnaire (HAQ) and 36-item Short-Form v2 (SF-36v2)and the second, the EDAQ only. We examined construct validity using Rasch analysis for the two components (Self-Careand Mobility) of the Dutch and German EDAQ. Language invariance was also tested from the English version. We examinedinternal consistency, concurrent and discriminant validity and test–retest reliability in the 14 EDAQ domains. The Self-Careand Mobility components satisfied Rasch model requirements for fit, unidimensionality and invariance by language. Internalconsistency for all 14 domains was mostly good to excellent (Cronbach’s alpha ≥ 0.80). Concurrent validity was mostlystrong: HAQ rs = 0.65–0.87; SF36v2 rs = − 0.61 to − 0.87. Test–retest reliability was excellent [ICC (2,1) = 0.77–0.97]. TheEDAQ has good reliability and validity in both languages. The Dutch and German versions of the EDAQ can be used as ameasure of daily activity in practice and research in the Netherlands and German- speaking countries